Australia’s karst regions-Where do they occur?As much as 15% of the Australian continent is made up of karst landscape.However, only 4% can be seen at the ground surface. This means a large number ofkarst landscapes are underground. Karst areas occur mostly along the southern, easternand western margins of the continent. The Nullarbor Plain is one of the largest karstregions in the world.

Other karst areas include:• Margaret River, Yanchep and Shark Bay (Western Australia)• Eyre Peninsula, Glenelg River (South Australia)• Buchan (Victoria)• Mole Creek (Tasmania)• Jenolan (New South Wales)

What is Karst?

Karst landscapes are shaped when surface or ground water becomes weakly acidicand reacts chemically with atmospheric or soil carbon dioxide. The dissolving actionsof water on limestone bedrock result in a distinctive landscape defined by depressionssuch as sinkholes, caves, holes and solution pipes.

How do karst environments affect us?

Knowing the location of karst features is important in making land use decisionsregarding roads, buildings and other structures. This information could prevent costlyrepairs to structures that are built on unstable karst landscapes and also reduce therisk of injury.

HHaazzaarrddssKarst terrain with caves, sinkholes and solution pipes inlimestone rock

Column Colmn28/A/93 /A/93 28/A/93

Photograph: Copyright Elery Hamilton-Smith

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Holes can occur in your backyard.Fence the hole and contact a specialistCopyright, 2001 Kentucky GeologicalSurvey, University of Kentucky

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Distribution of Karst in Australia ▲

What to do if you notice karsthazards:

• Contact your local council, emergency services or police

• Put a fence or protective barrier around the karst feature to preventinjury occurring

• Contact a specialist geologist or engineer

Geoscience Australia’s Risk Research Group aims to identify risk in order to improvecommunity awareness of natural hazards and to advance the community’s capabilityin making informed decisions in order to reduce the loss of life, property damage andeconomic disruption associated with these hazards.

To find out more about Natural Hazards look up Geoscience Australia

on the Worldwide Web at http://www.ga.gov.au/urban/ or by phoning

(02) 6249 9111.

www.ga.gov.au • GEOSCIENCE AUSTRALIA • www.ga.gov.auwww.ga.gov.au • GEOSCIENCE AUSTRALIA • www.ga.gov.au

KARST

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Australian Government

Preventative measures-Be aware!

• Ensure that housing and roads are not constructed on or near caves

• Leave a natural buffer of trees and understorey vegetation aroundsinkholes and caves

• Never dump rubbish in holes

• Reduce soil erosion, sedimentation and subsidence

• Vary sprinkler locations or water runoff locations – do not concentratewatering in one spot

• Promote vegetative land cover - bare ground leads to poor soilstructure enabling cavities to be exposed

Roads and houses should not be constructed near caves or sinkholes.Survey your land before you build.

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Tilted fences and cracks inbuildings are indicators ofpotential hazards.

Indicators of potential karst hazards:

• Slumping or sagging – tilting of fence posts or other vertical objects

• Structural failure – cracks along mortar joints and in pavements

• Rainfall ponding

• Vegetative stress – vegetation may become stressed due to lowering of the watertable

• Tree roots, stones and rocks become exposed

• The development of small rills and gullies

For positive identification, seek advice from your local government, specialist geologist or engineer.

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Hazards associated with karstfeatures include:

• Building failure – soil subsidence and caves represent a potential ground stabilityhazard to surface structures or engineering works.

Structural failure is often related to pre-existing cavities and voids.

• Groundwater contamination – rainfall runoff containing pollutants can contaminategroundwater as openings provide an easy and quick way for surface water to interactwith groundwater.

• Road collapse – roads built over caves or water pipeshave the potential to cave in. Fractures can occur incave roofs and excess water from burst or damagedpipes can gradually wash away soil within a cavity,forming a hole in the middle of a road.

• Sinkholes – sinkholes may occur due to varied landuse practices and can occur spontaneously. Smallsolution pipes are common, as are large caves.

Risk to individuals exists in karst areas, where thelandscape varies greatly.

• Cave collapse – compaction, blasting and vibrations can cause small fractures tooccur in the roof of caves. When the limestone’s cap rock is disturbed, its strength isweakened and structural failure can occur.

Key questions to ask prior todeveloping in known karst regions.

Land use planning is vital in karst regions and is the key to minimisingkarst risk to the community. In addressing karst risk, managers shouldbe asked the following:

• Will the proposed land use trigger sinkhole development?

• Will in-filled sinkholes remain inactive through the anticipated lifetimeof the proposed land use?

▲▲ Devegetated land is at higherrisk of karst collapse

Do not allow water to beconcentrated in one small zone

Road collapse at Linea,Northern Tasmania, Australia. Copyright: Elery Hamilton-Smith

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This sinkhole in Perth WA, developeddue to a burst water pipe in a gardenshed. A six metre hole developedovernight. The dashed line represents thehole that was filled in by a specialist.

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